Sea of Rhûn

Also called the Inland Sea, the Sea of Rhûn is located in eastern Middle-earth. It was a large inland sea located in Rhûn, a land east of Mirkwood and north of Mordor. The River Running (Celduin) from Erebor (the Lonely Mountain) and the River Redwater (Carnen) from the Iron Hills fed the Sea of Rhûn. The sea also contains an unnamed island that is about thirty miles along the southeastern and northwestern coasts and twenty upon the northeastern and southwestern coasts.

There were mountains on the southwest side of the sea and a forest on the northeast side. Wild white kine lived near its shores. The Great Horn of Gondor was made from the horn of one of these kine that had been hunted by Vorondil, a Steward of Gondor.

When Gondor was at the height of its power during the reign of King Hyarmendacil (TA 1015 - TA 1149), the realm extended east as far as the Sea of Rhûn. But as Gondor's power waned, Easterlings came into the area around the Sea of Rhûn and launched attacks on Gondor. In TA 1248, Minalcar (later called Romendacil) defeated an army of Easterlings between Rhovanion and the Sea of Rhûn and destroyed their settlements. In TA 1944, an army of Wainriders gathered on the southern shores of the Sea of Rhûn before launching an assault on Gondor that left King Ondoher dead.

During the War of the Ring, forces under the rule of Sauron mustered in the lands beyond the Sea of Rhûn. After the downfall of Sauron, Aragorn and Éomer rode beyond the Sea of Rhûn to flush out the last remnants of the enemy forces there.